PJM Operated Reliably Throughout Winter Storm Challenges

Record Level of Generation Outages


PJM shared its preliminary analysis of operating and market conditions during Winter Storm Elliott over the Christmas weekend in December, outlining how PJM and its members preserved the reliable flow of power and how market prices reflected system needs through record-breaking cold and unplanned generation outages.

The extreme weather through the weekend of Dec. 23–25, coupled with unusually high generation outages, resulted in a number of PJM emergency procedures, including the deployment of demand response to reduce load and an RTO-wide Call for Conservation, the first such appeal since the 2014 Polar Vortex.

Despite the advance planning for the winter storm by PJM and its members, the power supply mix was much tighter than PJM expected, PJM Sr. Vice President of Operations Mike Bryson told members at the Market Implementation Committee Wednesday.

“Quite frankly, while a lot of resources did perform well, generator forced outages were unacceptable,” Bryson said.

The Markets Team also outlined PJM’s Capacity Performance requirements and the preliminary work of outlining program penalties and bonuses as a result of generators that performed under their commitment or above their commitment.

Storm Preparation and Warnings

Donnie Bielak, Sr. Manager – Dispatch, first outlined the depth and breadth of the impact of Elliott, which has been dubbed a bomb cyclone and “historic Arctic outbreak” by the National Oceanic and Atmospheric Administration.

The storm, and then its associated frigid temperatures, impacted a large portion of the United States from the Northwest, Midwest, South and throughout the Northeast/mid-Atlantic regions; Christmas Eve would bring the lowest high temperatures on record for Dec. 24 for Washington, D.C., Philadelphia and Baltimore.

PJM saw an unprecedented 12-hour average temperature drop of 29 degrees on Dec. 23.

Bielak also described PJM’s extensive preparations for every winter, including data collection on fuel inventory, supply and delivery characteristics, emissions limitations, and minimum operating temperatures; meetings with federal and state regulators and neighboring systems to review winter preparations; and weekly operational review meetings with major natural gas pipeline operators.

In the days leading up to the storm’s arrival in the PJM footprint, PJM notified its members on Dec. 20 of the approaching frigid temperatures with a Cold Weather Advisory for the Western Region of the PJM footprint from Dec. 23 through Dec. 25. The advisory was expanded to the whole footprint on Dec. 22.

Introduced in 2022, a Cold Weather Advisory conveys expectations that PJM members will implement freeze protections, such as windbreaks, shelters or temporary heaters, and report operating limitations to PJM.

Cold Weather Alerts followed, first for the Western Region and then for all of the PJM region by Dec. 23. The Cold Weather Alert calls for specific measures to prepare for imminent weather, including review of deferrable maintenance, fuel limitations and enhanced communication with PJM, specifically regarding anticipated difficulties procuring fuel in the spot market that would result in unavailability of generation.

Conservative Approach

Going into the weekend, PJM forecasters were concerned about the unpredictability of demand given the extreme weather converging with the holiday weekend.

At the start of the day on Dec. 23, PJM had approximately 12,000 MW of forced (or non-planned) outages among its generation fleet. This heralded the start of a challenging day that would impose extraordinary demands on the PJM bulk electric system.

To account for the uncertainty of the conditions, PJM set up the operating day with 155,750 MW of available generation that Friday. That well exceeded the PJM load forecast peak of about 127,000 MW for the day. Friday’s actual peak load was approximately 10% above PJM’s forecast. Drivers of the load forecasting challenge included extreme cold temperatures, an unusually rapid temperature drop, and different load behavior than expected over a holiday weekend.

“We knew going into the operating day of Dec. 23 that our load model was going to have uncertainty, and that’s exactly why we made conservative decisions and took conservative actions with respect to generator procurement.” Bielak said.

Unprecedented Demand

Elliott was unprecedented for that time of year, given the severe temperature drop and resulting spike in load. The record-breaking plunge of 29 degrees over 12 hours on Dec. 23 surpassed the previous PJM record of a 22-degree drop during the 2014 Polar Vortex.

As cold weather gripped the PJM region Dec. 23 and power needs spiked, PJM began seeing high levels of forced generation outages. PJM implemented emergency procedures, including calls for synchronized reserves, an RTO-wide Maximum Generation Emergency Action and a call on demand response.

As temperatures fell, power demand rose to a peak of about 135,000 MW Friday evening. Around the same time, forced outages reached as high as 34,500 MW. Shortly before midnight Friday, PJM issued a Call for Conservation for the entire footprint, asking consumers to cut back on their energy use where possible between the hours of 4 a.m. on Dec. 24 through 10 a.m. on Dec. 25.

The demand continued after the peak on Dec. 23 and into Dec. 24. Even the valley, or low-point of demand, on Dec. 24 was significantly greater than any other peak, or high-point of demand, for that date in a decade.

The valley is crucial because that’s when PJM can usually cycle units offline and authorize owners to replenish the pond levels at their hydroelectric facilities, Bielak said.

“The (high level of) valley load combined with the high rate of forced outages that we were seeing during that time really made it impossible for us to do either of those two tasks to prepare for the upcoming morning peak.”

Generation outages further expanded to an initially estimated level of nearly 46,000 MW by Saturday morning. Factoring in a number of reserve generators that missed scheduled start times Saturday morning or operated at less than capacity, combined with PJM’s inability to replenish pumped storage based on the lack of availability of generators overnight, PJM was missing approximately 57,000 MW of its generation fleet by the morning peak of Dec. 24, the coldest day of the holiday weekend.

More than 90% of the forced outages came with no notice or less than one hour’s notice. That meant, Bielak said, that dispatchers were calling generators to bring them online, only to be told for the first time that the unit wasn’t available.

Emergency Procedures Preserve Reliability

Starting Saturday morning, more than 30 PJM members and stakeholders amplified PJM’s Call for Conservation through social and traditional media. Bielak said that the impact of consumers’ efforts seemed to work – electricity demand leveled off over the course of Saturday, and peak demand Saturday came in less than what was forecast.

Altogether, calls for conservation, a Maximum Generation Action and demand response are believed to have eased operating conditions through the Dec. 24 morning peak of about 129,000 MW and the evening peak that day of about 126,000 MW. As that Saturday continued, PJM also petitioned and received an order from the U.S. Department of Energy to ensure that certain generation units would remain available.[1]

PJM was able to come out of its Maximum Generation Emergency at 10 p.m. on Saturday night, meet the morning peak on Dec. 25, and end all emergency procedures at 10 p.m. Sunday.


Brian Chmielewski, Manager – Real-Time Market Operations, and Susan Kenney, Manager – Market Settlements Development, provided overviews of market operations during the Christmas weekend and the process of calculating Capacity Performance penalties and bonuses for generators.

Chmielewski said PJM’s review indicates that market prices accurately reflected the system conditions and needs through the event.

Kenney said generators were subject to 277 five-minute Performance Assessment Intervals over the 23 hours that emergency procedures were in effect on Dec. 23–24. During Performance Assessment Intervals, PJM measures generator performance in line with the capacity they have committed, and assesses penalties for under-performance and bonuses for over-performance. These requirements of PJM’s Capacity Performance program, instituted in the wake of the 2014 Polar Vortex, are intended to incentivize generators to better perform in extreme conditions.

Analysis of generators’ Capacity Performance requirements, including penalties and bonuses, are being refined and reviewed. Given the number of underperforming generators, Kenney said, very preliminary estimates of total penalties could be between $1 billion and $2 billion. Kenney cautioned that this estimate is provided as an initial reference point only and can change materially.

The calculation process will take several months, Kenney said, as PJM awaits Demand Response and Price Responsive Demand compliance data submissions, which are due Feb. 14. PJM will process excusals for generators as well as documentation of replacement generation provided by generators, which are allowed under Capacity Performance. The release of preliminary resource performance data is targeted for the first full week of February.

Given the potential for individual generators being subject to significant penalties, PJM is currently working through the billing timeline to account for any non-payment risk and PJM liquidity concerns, Kenney said. Additional information will be provided at the Jan. 24 Risk Management Committee meeting.

Bryson said that evaluating the effectiveness of Capacity Performance will be part of PJM’s comprehensive analysis of the events of Dec. 23–25. This review will also include analysis of impacts to energy and congestion markets and a review of extreme cold-weather load forecasting. PJM plans to report results, along with recommendations and actions, in April, Bryson said.

[1]Two generating units that fell under the DOE order ran at levels that exceeded their environmental permitting limits. The Department of Energy requires PJM to identify those generators, which were Bethlehem Energy in Bethlehem, Lehigh County, PA, and York Energy in Peach Bottom Township, York County, PA.